[time-nuts] Improving the stability of crystal oscillators

Hal Murray hmurray at megapathdsl.net
Sun Oct 14 23:18:07 EDT 2007

> I've heard there is some depth that building foundations need to be so
> they  don't get winter frost heave that might be on the order of a
> couple of feet,  but that's far different from an constant temperature
> depth.

That depends on where you live.

> I'm guessing that 10 or 15 feet may be required to get fractional
> degree temp  stability where I am.  The Wisconsin data was in loam
> which I think means a  fairly good insulator.  They had the widest
> temperature variation (15 c delta @  120 cm down).  I've got sand and
> clay after the first foot or so which may be a  better thermal
> conductor implying less variation. 

The math is the same as for skin depth on RF on metal.  The temperature 
fluctuation decays exponentially with depth.  Lower frequencies (years vs 
days) go deeper.

These are my opinions, not necessarily my employer's.  I hate spam.

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